Navigation vessels, such as craft of all types, caissons, hulls, rafts, toys and small models generally move over the water by sliding. This sliding introduces frictional forces which are all the greater when the immersed surface of the vessel is large and the speed of the latter increases.
In order to reduce the amount of friction, it is customary to give the hull a hydrodynamic profile which enables the layers of water in immediate contact with the hull to slide over the latter in a laminar way and therefore to avoid giving rise to eddies or whirlpools. However, although it is possible to eliminate the frictional forces for very low speeds of displacement of the vessel in this way, it is no longer the case when the speed increases, given that the re$istance to forward progress varies as a function of the square of the speed. The result of this is that a considerable fraction of the energy developed by the drive means used is employed to overcome friction and does not serve to drive the vessel.
Patents FR 387,781 and 984,997 disclose marine pleasure or leisure vehicles which partially remedy these drawbacks in that they are equipped with rotating floats which keep the hull entirely out of the water. These floats are equipped with a plurality of blades which are uniformly spaced along their periphery and which are more or less inclined with respect to the respective associated radial planes.
However, such vehicles still have a limited performance, in particular because of the high energy loss due to whirlpools created by the impact of the blades on the water surface. Therefore, in Patent FR 387,781, the floats have a hollow crown shape with a V-shaped cross-section. This shape introduces a loss of performance due to the friction of the water on the inner cylindrical wall of the float. With respect to the vehicle according to Patent FR 984,997, there are helical blades on its floats which achieve a vigorous stirring of the water and therefore a consumption of energy which is lost for driving the navigation vehicle.
Moreover, all known navigation vessels have a precise shape which cannot be modified in any way. A given vessel is therefore suitable only for a well defined use and gives a performance which cannot be changed. Builders are therefore obliged to produce not only all the conventional types of craft, such as motorboats, outboard motorboats, sailing boats, trimarans, catamarans, and the like, but also, for each of these types, models of different lengths and widths. Considerable sums have to be invested and this is naturally reflected in the purchase price. Moreover, this diversity of craft makes large-scale production difficult.
Patent EP 0,064,271 discloses a navigation vessel which as emerges from reading said patent, provides a modular-structure which has no aim other than to enable the modules to be nested in one another in order for it to be possible to transport the vessel in a small space, for example in a trailer towed by a motor vehicle or on the roof of the latter. However, nowhere is it suggested in this patent that the vessel may be converted into other types of vessel. The shape of the modules used does not, moreover, lend itself to such a conversion.